shm_open and shm_unlink not detected on openSUSE Linux

The test in libraries/unix/configure fails to detect shm_* functions on openSUSE. The -lrt flag is passed as part of CFLAGS rather than in LIBS and so it appears before the object file referencing the shm_* function.

Note: The openSUSE linker sets --as-needed by default and hence the order of linker options does matter.